In order to study the fluid transport mechanism across corneal endothelium, the electrical properties of the layer are being determined. The low electrical resistance of the tissue made advisable to adapt and develop specific techniques for this purpose, such as the determination of the impedance of the layer. The endothelium has been found to display both capacitive and inductive reactance. The relationship between these parameters and the transport of fluid is being studied; this transport is also being correlated with the equivalent "short-circuit" current calculated from the impedance data, which is assumed to be an excellent indication of the condition of the ionic transport mechanisms which may underlie the fluid movement. Models recently proposed for the active and passive endothelial properties are being developed further and tested.